Now Trewin Restorick of Business Green is weighing in, asking how we might discover a consumption condom. His point is that many environmentalists seem to skirt around the topic of population because they believe it is too difficult to address, preferring to focus on consumption instead. Yet, he argues, the answers to population—education, economic development, women's empowerment and access to birth control—are actually well established. It's how to tackle consumption that we are still stumped on. As always, this really isn't an either/or question—both need to be tackled urgently. But it's good to see Restorick putting it in perspective.

From one African activist's insistence that family planning helps women and the environment, to asking whether voluntary birth control is the cheapest answer to climate change, population seems to be a recurring theme in the blogosphere lately.